1. Field of the Invention
The present invention relates to medicine, and in particular, to cardiovascular surgery and is designed for replacement of affected natural heart valves during cardiac surgery.
2. Description of the Related Art
There are many designs of heart valves prostheses used for replacement of natural valves: ball, frameless, single leaflet, bi-leaflet, tri-leaflet prostheses. Widely used implanted frame prostheses are very reliable and ensure satisfactory hemodynamics, appropriate improvements reduce acoustic noises, anxiety of patients, increase the time of continuous operation. Standard prostheses include a ring-shaped body providing a channel for the flow of blood. Installed in the body is one or more leaflets configured for the alternation of an open position for the passage of a direct flow of blood and a closed position for the closure of the channel and restriction of a reverse flow of blood. In addition, the heart valve prosthesis contains a coupling arrangement for the connection of the valve body with surrounding heart tissues. Basically, this arrangement is made in the form of a cuff which is sewed to the heart tissues and envelopes the lateral surface of the prosthesis valve body.
Research and engineering activity have been permanently carried out for the creation of new designs of valve prostheses and modernization of existing ones by means of improvement of their features.
Efforts to increase the efficiency of heart valve prostheses are continued. The efficiency of the heart valve prosthesis is determined by the area of the flow section when the leaflets are in the open position. The valve body of the prosthesis sewed in with the help of the cuff into place of a removed natural valve has a certain thickness reducing the flow section, the leaflets exhibiting resistance to the flow and partially closing a passage opening, especially when positioned centrally. The effective area of the valve flow section is thus reduced, which is one of the main critical factors of the heart valve prostheses. This is particularly dangerous in valves of small diameters.
Known from the prior art have been artificial heart valves which eliminate this disadvantage to a certain extent—these are the valves with an increased flow section and central positioning of leaflets upon the opening of the valve (see e.g. U.S. Pat. Nos. 6,007,577, 6,176,877, 6,719,790). The increase of the flow section in these prostheses is achieved by making the valve body with a flow section one size up (by approx. 2 mm) as compared with a regular valve, a cuff of a special design ensuring the installation of such valve into a position over the excised natural one. Thus, the thickness of the prosthesis body does not change the flow section of the valve, which remains equal to that the natural valve used to have.
However, a problem of hemodynamics distortion stays unsolved for such artificial valves. Indeed, the leaflets in the open position of the valve stay in the central area of the velocity profile distorting it and reducing the blood flow velocity through the valve.
A number of designs is known (see U.S. Pat. No. 4,274,437, RU 2066984) where the main flow section is provided in the center. It is obvious in such a design that the central part of the flow through the valve remains weakly disturbed and the distortions caused by the leaflets are minimal. However, these valves have no practical application in surgery because of low reliability and high probability of the falling out of the leaflets. As it turned out, the central problem was designing such leaflet traveling stops, which could reliably hold the leaflets during the whole life of the valve and contribute to its continuous operation.
So a need for a new design of the heart valve prosthesis combining the reliability and undistorted hemodynamics of the blood flow is obvious.
The closest analog for this invention is an artificial heart valve (RU 2066984) containing a ring-shaped body and two leaflets placed therein with a possibility of turning between top and bottom stops in relation to the blood flow and of forming the main zone of the flow section in the center, the zone being limited by round sections of inner walls of the body and bottom edges of the leaflets in relation to the blood flow, the bottom stops of each leaflet including a pair of half-axles installed near the periphery of the valve section and the top stop of each leaflet including a rest, the end of which is located in a groove of the rectangular cross-section made on a leaflet peripheral edge facing the rest.